Washing machine with water control and associated method

ABSTRACT

An automatic washing machine with water level control and associated method. In one embodiment, the washing machine comprises a tub for receiving a load of clothes, a water level sensor taking water level measurements during a water fill stage, and a controller. The controller controls a water valve that introduces water into the washing machine. The controller comprises a timer, a memory and a microprocessor. The microprocessor accesses a signature fill rate of the washing machine when unloaded, receives water level measurements from the sensor during the fill stage, and determines a measured fill rate. The microprocessor compares the measured fill rate to the signature fill rate and shut off the water valve when the measured fill rate is substantially equal to the signature fill rate.

FIELD OF THE INVENTION

The present invention relates to a washing machine having a water levelcontrol and associated method.

BACKGROUND OF THE INVENTION

Many household appliances, such as, for example, clothes washers anddishwashing machines are equipped with water conservation devices,including water level controls. These devices may require user input inthe form of selection of a cycle type, or cycle duration or estimate ofwater level required based on the load.

Conventional top-load washing machines, for example, include a pressureswitch that is either fixed or variable to determine the water levelwhen filling the washing machine. In a variable pressure switch, theuser controls and may vary the fill water level by selecting a settingon an associated dial every time the washing machine is used. Often,however, the user guesses incorrectly the appropriate fill level orfails to reset or adjust the water level for each clothes load. Thisleads to over-consumption of water and inefficient energy use forheating the water.

Federal regulations provide manufacturer incentives, for example in theform of energy credits, to develop more water and energy efficientmachines, reducing hot water consumption. Recognizing that reliance onthe user to correctly determine and remember to reset the water levelswitch is not an effective method to conserve energy, regulatoryagencies do not give credits toward energy use limits to manufacturersof washing machines that have user-controlled water level features.

Therefore, water-conserving washing machines that do not rely on theuser to determine the water fill level are desirable.

SUMMARY OF THE INVENTION

In one embodiment, the invention provides a method for controlling awater fill level of a washing machine. The method comprises loading thewashing machine with a wash load, initiating a water fill stage,counting the water fill time, and measuring the water level. A measuredfill rate is determined from the measured water level and water filltime, and compared to a signature fill rate, which is characteristic ofthe washing machine when unloaded. When the measured fill rate is equalto the signature fill rate, the water fill stage is terminated.

Another embodiment of the invention provides a washing machine thatcomprises a tub for receiving a load of clothes, a water level sensortaking water level measurements during a water fill stage, and acontroller. The controller controls a water valve that introduces waterinto the washing machine. The controller comprises a timer, a memory anda microprocessor. The microprocessor accesses a signature fill rate ofthe washing machine when unloaded, receives water level measurementsfrom the sensor during the fill stage, and determines a measured fillrate. The microprocessor compares the measured fill rate to thesignature fill rate and shut off the water valve when the measured fillrate is substantially equal to the signature fill rate.

Another embodiment of the invention provides a method for controlling awater fill level of a washing machine. The method comprises measuring afill rate of the washing machine during a water fill stage when themachine contains a wash load in an inner tub. The measured fill rate iscompared to a predetermined signature fill rate of the washing machinewhen unloaded, and the water fill stage is terminated when the measuredfill rate is equal to the signature fill rate.

Yet another embodiment provides a method for controlling a water filllevel of a washing machine. The method comprises turning on a watervalve to start a water fill stage, monitoring a water fill rate duringthe water fill stage, measuring fluctuations in the water fill rate,determining a steady state fill rate, and turning off the water valve.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. Moreover, in the figures, likereference numerals designate corresponding parts throughout thedifferent views.

FIG. 1 is a partially cut-away perspective view of a washing machineaccording to the present invention;

FIG. 2 is a partial sectional view of the washing machine of FIG. 1;

FIG. 3 is a flow chart of the controller logic according to the presentinvention;

FIG. 4 is a schematic control diagram according to the presentinvention; and

FIG. 5 is a representative graph of water level versus fill time.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following description of preferred embodiments is merely exemplaryin nature and is in no way intended to limit the invention, itsapplication, or uses.

FIGS. 1 and 2 illustrate an embodiment of the washing machine 100according to the invention. The washing machine includes a housing 110,an inner tub 102, and an outer tub 104. The inner 102 tub includesperforations 107 through which water enters the inner tub 102 from theouter tub 104. The inner tub includes an agitator 106 connected to amotor and transmission system 108. A wash load 112 is introduced intothe inner tub 102 for washing.

Referring to FIGS. 1 and 4, the washing machine includes a controlconsole 116 with a user-operable control panel 114. The control console116 houses a controller 118, which includes a microprocessor 120,storage memory 140, and a timer 142. The controller 118 receives a userinput 122 through the control panel 114. The user input 122 includeswash cycle selection and wash cycle modifiers, such as wash and/or rinsetemperature and clothes type. The controller 118 controls the watervalves 124 to turn water flow on and off and to adjust the hot and coldwater flow for a user-selected temperature setting.

The controller 118 communicates with a water level sensor 126. The waterlevel sensor 126 may be a continuously variable water level sensor 130,such as a commercially available LL series sensor from Honeywell Sensingand Control, Milpitas, Calif., or any other type of water level sensor,including a commercial radio frequency sensor, a proximity sensor, andthe accurate radio frequency sensor disclosed in copending U.S. patentapplication Ser. No. ______, entitled “Liquid Level Sensor for Applianceand Associated Method”, which is incorporated herein by reference in itsentirety. The radio frequency sensor 128 is mounted on the outer tub104. The water level sensor 126, 128 is programmed to periodically, forexample at preset time intervals, or continuously check the water level,and send an analog or digital signal that indicates the water level tothe microprocessor 120 of the controller 118.

In operation, the user loads the washing machine 100 with the wash load112 and initiates a washing cycle using the control panel 114. It isunderstood that any complete wash cycle includes a water fill stage. Theuser's input is conveyed from the control panel 114 to the controller118, which controls the progression of the washing cycle. At the waterfill stage, the controller 118 opens the water valves 124 and startscounting fill time as water enters the outer tub 104. The first fewseconds of the fill time up to “t₁” correspond to filling the lowerportion 132 of the outer tub 104 up to a water level “H₁”, as shown in arepresentative graph of water level versus fill time in FIG. 5. Theinitial fill time up to t₁ depends on each machine's geometry and thewater pressure, and can be typically about 20-30 seconds. The initialportion of the graph up to time t₁ is substantially linear, and,therefore, the slope of the graph, which represents the fill rate and isequal to tan α₁, is substantially constant. During this part of the fillstage, the controller 118 may calibrate the washing machine 100 toeither determine and store in memory 140 the initial fill rate tan α₁,or modify a fill rate tan α₂, which is factory-set. As water startsentering the inner tub 102, water eventually reaches the wash load 112.The wash load 112 gradually absorbs water and possibly reorients itselfunder the weight of the absorbed water, thus affecting the fill rate andgenerally interacting with the water level to cause nonlinearfluctuations in the fill rate. The water level versus fill time graphis, therefore, non-linear during this part of the water fill stage,until the wash load 112 is fully submerged in water, at time t₂corresponding to water level H₂. After time t₂, that is, after fullsubmersion of the wash load 112, the water level versus fill time graphbecomes linear again, with slope defined by tan α₂, where α₂, and α₂ aretypically equal or have a known relation, which can be used forcalibration purposes. The actual values of the slope tan α₁ and tan α₂,are characteristics of the geometry and dimensions of the inner tub 102,the outer tub 104 and other features of the washing machine 100, andprovide a signature for the washing machine 100. Each washing machine'ssignature can be determined by the manufacturer and stored in themicroprocessor 120 at the factory. The signature fill rate can also bemodified during calibration as described above.

To promote full submersion of the wash load 112 during the water fillstage, the controller 118 periodically actuates the agitator 106 duringthe fill time between t₁ and t₂. The agitator 106 causes the wash load112 to be more evenly distributed and uniformly wetted inside the innertub 102. Thus, sudden discontinuities or spikes in the water level andfill rate are minimized or avoided, increasing the reliability of thewater level measurements.

The microprocessor 120 receives the water level data from the waterlevel sensor 126 and determines a measured fill rate, which isrepresented by tan β at time t₃, where t₃ is a representativemeasurement time between t₁ and t₂ in the graph of FIG. 5. When themeasured fill rate at time t₂ becomes substantially equal to thesignature fill rate tan α₂ which is factory preset or modified duringcalibration from tan α₁, the wash load 112 is fully submerged and thecontroller 118 shuts off the water valves 124 and terminates the waterfill stage.

A flow chart of the water level control is depicted in FIG. 3. Theprocess starts at 150 with user input, the wash cycle progresses to thewater fill stage at 152, and the controller 118 turns on the watervalves 124 and begins counting time at 154. The sensor 126 measures thewater fill level and communicates with the controller 118 at 164. Thecontroller 118 determines the fill rate at 156. The measured fill rateis compared with the signature fill rate tan α₂ at 158. If those twovalues are not equal, the process continues. If those values are equal,the controller 118 turns off the water valves 124 at 160 and the washcycle continues. In one embodiment, the controller may perform acalibration at 157 to determine or modify the signature fill rate tanα₂, by determining tan α₁ and using the known relation between α₁ andα₂.

It will be appreciated that the water level versus time graph of FIG. 5is merely illustrative. The shape and the characteristics of the graphdepend on a variety of factors, which may include, in addition to thedimensions and shape of the inner and outer tubs 102, 104, watertemperature and water pressure. The water fill rate generally includesan initial stage for the time interval from 0 to t₁ a transient stagebetween t₁ and t₂, and a steady state beyond t₂. The controller 118monitors the fill rate until a steady state is reached at t₂, and atthat time, it shuts the water valves 124. The onset of the steady statecondition can be determined by comparing the measured fill rate to asignature fill rate as discussed above, or by determining that the fillrate ceases to fluctuate and remains substantially constant.

While various embodiments of the invention have been described, it willbe apparent to those of ordinary skill in the art that other embodimentsand implementations are possible that are within the scope of thisinvention. Accordingly, the invention is not restricted except in lightof the attached claims and their equivalents.

1. A method for controlling a water fill level of a washing machine, themethod comprising: loading the washing machine with a wash load;initiating a water fill stage; counting the water fill time; measuringthe water level; determining a measured fill rate from the measuredwater level and water fill time; comparing the measured fill rate to asignature fill rate characteristic of the washing machine when unloaded;and terminating the water fill stage when the measured fill rate isequal to the signature fill rate.
 2. The method of claim 1, whereinmeasuring the water level includes obtaining water level measurementsusing a water level sensor.
 3. The method of claim 1, further comprisingagitating the wash load.
 4. The method of claim 1, further comprisingpresetting the signature fill rate.
 5. The method of claim 1, furthercomprising modifying the signature fill rate by determining a fill rateduring an initial portion of the water fill stage.
 6. The method ofclaim 5, wherein determining the fill rate during the initial portion ofthe water fill stage comprises: counting the water fill time during theinitial portion of the water fill stage; and measuring the water levelduring the initial portion of the water fill stage.
 7. The method ofclaim 1, further comprising calibrating the washing machine by modifyingand storing the signature fill rate.
 8. The method of claim 4, furthercomprising calibrating the washing machine by modifying and storing thesignature fill rate.
 9. An automatic washing machine comprising: a tubfor receiving a load of clothes; a water level sensor operable to takewater level measurements during a water fill stage; and a controllercontrolling a water valve that introduces water into the washingmachine, the controller comprising a timer, a memory and amicroprocessor, wherein the microprocessor accesses a signature fillrate of the washing machine when unloaded, receives the water levelmeasurements from the sensor during the water fill stage, themicroprocessor being programmed to determine a measured fill rate,compare the measured fill rate to the signature fill rate and shut offthe water valve when the measured fill rate is substantially equal tothe signature fill rate.
 10. The washing machine of claim 9, wherein thewater level sensor is a continuously variable pressure sensor.
 11. Thewashing machine of claim 9, wherein the water level sensor is aproximity sensor.
 12. The washing machine of claim 9, wherein the waterlevel sensor is a radio frequency sensor.
 13. A method for controlling awater fill level of a washing machine, the method comprising: measuringa fill rate of the washing machine during a water fill stage, themachine containing a wash load in an inner tub; comparing the measuredfill rate to a signature fill rate of the washing machine when unloaded;and terminating the water fill stage when the measured fill rate isequal to the signature fill rate.
 14. The method of claim 13, furthercomprising agitating the wash load.
 15. The method of claim 13, furthercomprising: calibrating the washing machine before water reaches thewash load in the inner tub; and modifying the signature fill rate bydetermining a fill rate during an initial portion of the water fillstage.
 16. The method of claim 15, wherein determining the fill rateduring the initial portion of the water fill stage comprises: countingthe water fill time during the initial portion of the water fill stage;and measuring the water level during the initial portion of the waterfill stage.
 17. The method of claim 15, further comprising presettingthe signature fill rate in the machine.
 18. A method for controlling awater fill level of a washing machine having a wash load, the methodcomprising: turning on a water valve to start a water fill stage;monitoring a water fill rate during the water fill stage; measuringfluctuations in the water fill rate; determining a steady state fillrate; and turning off the water valve.
 19. The method of claim 18,wherein determining a steady state fill rate comprises measuringsubstantial ceasing of fill rate fluctuations.
 20. The method of claim18, wherein determining a steady state fill rate further comprises:comparing the monitored water fill rate to a predetermined fill rate;and determining that the monitored water fill rate is substantiallyequal to the predetermined fill rate.